Automatic switch



y June 25, 1940. v D, wRlGHT v2,205,558?

AUTOMATIC SWITCH Filed March 27, `1937 1 liv/M INVENTOR DEN/s WRIGHT Patented June 25, 1940 UNITED As-rares PATENT orifice 'AUTOMATIC SWITCH f Denis Wright, Liverpool, England, assignor to Associated rI Ieleplione & Telegraph Company, Chicago, Ill., a corporation efDelaware Application March 27, 1937, f'Serial No. .133,338 1 .I-n Great Britain April 6, 1936 claims. (c1. ,20o-166) .turbance of the contactv between the `wiper .tip

and the fixed kContact is likely to give rise to microphonic noises if the circuit in which the wiper is .connected carries speech currents. In practice in a telephone installation a number of switches and their associated contact banks may be mounted side by side on. a shelf member and the actuation of anyone switch will communicate vibration to the other switches. So long as the frequency and phase of the vibrations produced are the same for any switch and its associated contact bank, no micro'plionic noise will be produced since there ,will be no relative movement between the switch wipers and the particular bank contact upon which they are rest-VV ing.` Due probably to the bearing clearances required however, a switch shaft in a disturbed 'switch will tend to execute mechanical vibrations which may differ from those imparted to the switch as a whole and if therefore the wiper assembly is rigidly fixed to the shaft, vibration imparted to it through the shaft which differs in frequency from that imparted to the contact bankand the switch as ar whole will result in variation of contact pressure with a likelihood of resulting microphonic noise.

According to the invention this trouble is overcome in that the support for the wipers is q loosely mounted on the wiper carriage by means of a connection which does not transmit mechanical vibration. According to a further feature of the invention this connection involves the use oi a lm of oil or similar liquid whereby the two members are mechanically insulated from one another.

The invention will be better understood from the following description of one method of carryingit into effect, reference being had to the accompanying drawing comprising Figs. 1 and 2. Fig. 1 shows a perspective viewof a wiper assembly suitable for a vertical and rotary switch and of the so-called linked-tip type which is described in detail in R. N. Saxbys application, Serial No. 76,375, iiled April 25, 1936. Fig. 2

shows a vertical cross-sectional view of the wiper assembly along the line A--B in Fig. Y1. This figure .serves toshow more clearly the vmethods 'adopted for securing 'that the wiper support is` mechanically insulated from theA carriage. H5 It will be seen `from the Ydrawing that the wiper `assembly is ymounted on a flat plate member AIl',

loosely supported by means of a flanged screw, I'I

lfrom the upper plate member I6 vone end of which is bent overand so shaped as to co-oper- :to ate with the semi-circular bracket .member I8 in order to .provide `a suitable clamping `means to the tubular wiper carriage or shaft of the switch. The wiper blades Il) and 'II are mounted ,onopposite sides of `a plate of ,insulating 'matellt rial I3, the complete wiper assembly being se-v cured to the lower plate I5 by two screws I4 and insulating 'Washers 20. The insulating plate I3 is extended forwardly between the wipers so as to prevent contact between them and also serves Si!) v to limit any Vibration which may developduring vertical stepping owing to the extreme flexibilityv of the blades. Each of the blades is formed as a single pressing of brass or lother suitable material while the tips are spoon-shaped so' minimise f r wear and the possibility of catching contacts in adjacent levels. Furthermore the blades are linked together at their free ends by means of an insulating washer I2 which tends to localise the pressure at the tips so that it is maintained sub- :i0 stantially constant on both blades over an appreciable arc of movement of the blades about an axis transverse to the shaft. The extent of movement is limited by the insulating member I3 which is provided also with suitable slots and 35 holes to secure the wiper cords whichv are Wired to the wiper terminal tags I9.

The xing screw I1 is provided with a flange which prevents it being screwed completely home and projections on one member engaging in holes 40 y in the other ensure the proper relative position of the two parts. Conveniently this positioning is effected as shown by the heads of the wiper assembly fixing screws I4 which are arranged to be a'loose fit in the centreing holes of the upper 45 supporting plate member I6. As shown in Fig. 2 there Will be perceptible play between the upper and lower plates which allows of slight relative a bank contact is reduced to a minimum whereby eliminating microphonic noise.

I claim:

l. In a rotatable switch shaft wiper assembly, a plurality of wiper springs, a mounting member for said springs, a second member, means for mounting said second member on a switch shaft, means for loosely mounting said rst memberV on said second member, said loose mounting providing space between said members, and a film of oil filling said space so that said members are mechanically insulated from one another to prevent vibrations of said second member from being transmitted to said wiper springs.

2. In a wiper assembly for a rotatable switch shaft, a plurality of springs, a plate for mounting said springs, a mounting bracket, a shoulder screw, said mounting bracket having an opening larger than the diameter of the shoulder of said screw and having thickness less than the length of said shoulder, said screw having a head larger than the diameter of said opening and screwed into said plate so that the shoulder portion of the screw contacts the surface of said plate, said mounting bracket having its surfaces covered with a film of oil to prevent mechanical vibrations from being transmitted between said mounting bracket and said plate.

3. In a wiper assembly for a rotatable switch shaft, a plurality of springs, a plate for mounting said springs, a mounting bracket, a shoulder Screw, said mounting bracket having an opening larger than the diameter of the shoulder of said screw and having thickness less than the length of said shoulder, said screw having a head larger than the diameter of said opening and screwed into said plate so that the shoulder portion of the screw contacts the surface of said plate, said mounting bracket having its surfaces covered with a film of oil to prevent direct contact with said screw and said plate.

4. In an automatic switch wherein a wiper shaft is operated to select bank contacts, a Wiper assembly comprising a plurality of wiper springs, a plate, means for rigidly clamping said springs to said plate, a mounting bracket, means for rigidly clamping said mounting bracket to the shaft of the automatic switch, means for loosely mounting said plate on said bracket, said loose mounting providing a space between the plate and the bracket, and vibration absorbing means in said space to prevent vibrations of said shaft from being transmitted to said springs.

5. In a Wiper assembly used in the selection of bank contacts by an automatic switch, a pair of wipers, a plate, means for rigidly fastening said springs to said plate, a mounting bracket, means for rigidly mounting said bracket to the shaft of an automatic switch, a fluid carried by said bracket, and means for floatingly supporting said plate on said fluid to prevent vibrations of the switch shaft from being transmitted to said wipers.

6. In a wiper assembly as claimed in claim 5, wherein the floating support of said plate permits longitudinal and lateral movement of the plate with respect to said mounting bracket and means for limiting the extent of such movement.

DENIS WRIGHT. 

